1. Field of the Invention
This invention relates to an improved process for the production of hydrocarbons from carbon monoxide and hydrogen. In one aspect, this invention relates to a catalyst for use in the process to produce hydrocarbons containing two to four carbon atoms.
2. Description of the Prior Art
The art contains many examples of metals known to be useful in reacting carbon monoxide with hydrogen to produce a variety of compounds -- both hydrocarbons and oxygenated compounds. These metals include, among others, Mo, W, Th, Ru, Re, Pt, Ni, Co, and Fe. It is upon the last two of these metals that most commercial experience is based. In what has come to be called the Fischer-Tropsch synthesis, carbon monoxide and hydrogen are reacted over an iron or cobalt catalyst to produce saturated and unsaturated hydrocarbons and oxygenated compounds containing from about one to as many as one thousand carbon atoms. The hydrocarbons can be aliphatic, alicyclic, or aromatic. Commercial utilization of this Synthesis prior to 1950 was accomplished largely in Germany and is summarized in Storch, Columbic, and Anderson: The Fischer-Tropsch and Related Synthesis, John Wiley and Sons, New York 1951.
The following references are illustrative of the prior art and are helpful to an understanding of Applicant's invention:
Schultz, John Floyd, "Noble Metals, Molybdenum and Tungsten in Hydrocarbon Synthesis", by J. F. Schultz, F. S. Carn, and R. B. Anderson. (Washington) U.S. Dept. of the Interior, Bureau of Mines Report 6974 (1967).
Anderson, R. B., "Fischer-Tropsch Synthesis", by R. B. Anderson, B. Seligman, J. F. Schultz, R. Kelly, and M. A. Elliott. Industrial and Engineering Chemistry, Vol. 44, No. 2 (1952).
West German Pat. No. 2,343,032 "Process for Controlling Fischer-Tropsch Synthesis", Inventor: Dr. Mark Eberhard Dry, Priority Date: Sept. 5, 1972.
Mills, G. Alex, and Fred W. Steffgen, "Catalytic Methanation", Catalysts Review, Vol. 8, pages 159-210 (1973).
Dry, M. E., T. Shingles, L. J. Boshoff, and G. J. Oostehurzen, "Heats of Chemisorption on Promoted Ion Surfaces and the Role of Alkali in Fischer-Tropsch Synthesis". Journal of Catalysis, Vol. 15, pages 190-199 (1969).
Pichler, Helmet and Annemarie Hector, "Carbon Monoxide-Hydrogen Reactions", Encyclopedia of Chemical Technology Vol. 4 (2nd Edition) pages 446-489.
Weitkamp, A. W., Herman S. Seelig, Norman J. Bowman, and William E. Katy, "Products of the Hydrogenation of Carbon Monoxide Over an Iron Catalyst", Industrial and Engineering Chemistry, Vol. 45, No. 2, pages 343-367 (1953).
U.S. Pat. No. 2,490,488 "Hydrocarbon Synthesis Catalyst", Inventor: S. Grant Stewart; Issued: Dec. 6, 1949.
As mentioned above, the most extensive commercialization of the Fischer-Tropsch synthesis has been with the use of either an iron or a cobalt catalyst. Such catalysts produce a potpourri of saturated and unsaturated aliphatic and aromatic hydrocarbons as well as oxygenated compounds which for the most part contain more than four carbon atoms. The cracking of these compounds to produce ethylene and/or propylene is not very efficient. For this purpose the desired compounds are ethane, propane, and the various isomers of butane and butene. In addition sulfur impurities such as hydrogen sulfide, carbonyl sulfide, or any other sulfur compound deactivate iron and cobalt catalysts in concentrations as low as 0.1 ppm.
Schultz has shown molybdenum to have some sulfur resistance. His work was directed toward the development of an efficient catalyst to produce methane from carbon monoxide and hydrogen and he was reasonably successful. However, methane is not the preferred feedstock for the production of ethylene and/or propylene. For the present purposes, the catalysts of iron and cobalt produce molecules containing too many carbon atoms, and the catalysts tested by Schultz produce molecules containing too few carbon atoms.
The present invention relates to a process which produces molecules containing a more desirable number of carbon atoms for use as ethylene cracker feedstocks. Typical catalysts in use today for this reaction require lowering of the concentration of sulfur impurities to approximately 0.1 ppm. Since it is expensive to decrease the concentration of sulfur impurities to a level of approximately 0.1 ppm, development of a catalyst usable at a higher concentration would result in considerable savings in investment and operating costs in a commercial facility. The catalyst of the present invention can be employed with a higher concentration of sulfur impurities in the feedstock. The catalyst of the present invention does not require precious metals and is capable of sustained operation at a hydrogen to carbon monoxide ratio of one to stimulate formation of the saturated and unsaturated hydrocarbons containing from two to four carbon atoms.